The benefits of mammalian hibernation have been well documented. However, the physiological and ecological costs of torpor have been emphasized only recently as part of a hibernation-optimization hypothesis. This hypothesis predicts that hibernators with greater availability of energy minimize costs of torpor by less frequent utilization of torpor and by maintaining higher body temperatures (T(b)) during torpor. In order to further examine the relationship between body mass and other parameters of hibernation, we present data, collected over a 12-year period, on the hibernation patterns of free-living woodchucks (Marmota monax) in southeastern Pennsylvania. Body mass was positively correlated with T(b) and negatively correlated with percentage of the heterothermic period spent in torpor. Thus, woodchucks with greater mass exhibited less time in torpor as a proportion of their heterothermic period and at higher T(b) than those with lesser mass. This strategy potentially enhances the physiological and physical ability of woodchucks to defend territories, avoid predation, find mates, and complete the reproductive cycle upon emergence from hibernation. Our results further support the hibernation-optimization hypothesis by demonstrating the relationship between body mass and characteristics of torpor and contributing toward a fuller understanding of this concept.

There is little information on the phenotypic flexibility of hibernation characteristics within species. To address this issue, we observed differences in hibernation characteristics of three free-ranging populations of woodchucks (Marmota monax) distributed along a latitudinal gradient from Maine to South Carolina. Data from free-ranging animals exhibited a direct relationship between latitude and length of the hibernation season. As expected, woodchucks in the northern latitudes hibernated longer than those in the southern latitudes. Also, the length of interbout arousals decreased with increase in latitude, whereas the length of torpor bouts and the number of arousals increased. Thus, we observed phenotypic plasticity in hibernation characteristics based primarily on latitudinal temperature differences in each population. Further analysis revealed a direct relationship between latitude and total time spent in torpor. Maine animals spent 68% more time in torpor than South Carolina animals. However, total time spent euthermic did not differ among the three populations. The "cost-benefit" hypothesis of hibernation may help to explain these results. It assumes that hibernators avoid the physiological stress of torpor by staying euthermic as much as possible. Woodchucks in each population maximized time spent euthermic, utilizing torpor only at the level needed to survive winter hibernation and to commence reproduction in the spring.

No abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology.Abstract. Field and laboratory investigations were conducted to determine the major seasonal adaptations exhibited by the collared peccary (Tayassu tajacu) in the desert. Emphasis was placed on the animal's thermoregulation, water relations, and energy requirements under changing environmental conditions. Body core temperatures were labile and ranged from 37.5?C to approximately 40.9?C during both winter and summer seasons. Skin temperatures were always above ambient and reached a high of 49.2?C during summer. Heat loss across the skin of summer animals averaged 0.041 cal/cm2 * min during the day and 0.038 cal/cm2 * min at night. Winter animals by basking exhibited a slight heat gain during the day (0.033 cal/cm2 min) but lost heat at a rate of 0.223 cal/cm2 * min at night.The pelage of the peccary had a poor insulative value; thermal conductance equaled 0.291 cal/cm2 * hr * C. Summer animals became lighter in color over certain parts of their body and also decreased density of bristles over most of their body.Total water requirement for summer peccaries was 66.5 ml/kgday and for winter peccaries 38.6 ml/kg-day. Respiratory evaporation was the major avenue of water loss and accounted for 6.1% of body wt/day for summer dehydrated peccaries. During dehydration peccaries were able to reduce evaporative water loss by as much as 68% and urinary water loss by 93%, but were unable to produce dry feces. Their maximum osmolar urine/plasma ratio was 4.0.Total daily energy requirement for an 18.2 kg peccary was 794.05 Kcal/day in summer and 916.96 Kcal/day in winter. The annual energy requirement was estimated at 17,166 Kcal/kg * year. On the basis of these calculations, a herd of 25 individuals occupying a home range of 388 ha at the Three-Bar Wildlife Area would require approximately 20% of the annual production of prickly pear cactus (7,985.0 kg/year or 20,130.9 Kcal/hayear). 1 deserts have been restricted to smaller mammals, particularly desert rodents and hares. Relatively little physiological work has been done with the few medium to large size mammals that inhabit deserts of the American Southwest. Mammals in this category include the desert bighorn sheep, desert mule deer, mountain lion, collared peccary, and a number of canids.The collared peccary or javelina (Tayassu tajacu) was selected for study because of its intermediate size and the need for information on its adaptational physiology by management personnel attempting to improve the animal's status as a game species in the Southwest. The collared peccary ranges from South and Central America to its most northern extens...

No abstract

No abstract

No abstract

No abstract